Gaza City (CNN) — The Israeli military launched a ground operation into Gaza late Thursday following some of the most intense fighting of the 10-day face-off between Israel and Hamas.

Israeli Prime Minister Benjamin Netanyahu and Defense Minister Moshe Yaalon ordered the ground action to destroy tunnels from Gaza into Israeli territory, according to a statement from the prime minister’s media adviser.

The adviser said Hamas terrorists used such a tunnel to infiltrate Israel on Thursday morning to launch an attack, but that the Israel Defense Forces thwarted the action. The IDF was told to be ready to expand the action, called Operation Protective Edge, the statement said.

Hamas spokesman Fawzi Barhoum told CNN that “the beginning of the Israeli ground invasion of Gaza is a dangerous step with unknown consequences. Israel will pay a heavy price for it.”

The long-awaited ground operation follows one of the worst nights of fighting since the war began. That fighting began after a temporary cease-fire ended earlier in the day.

Gaza hospital struck

The Gaza Health Ministry said seven children were killed in three hours.

The IDF dropped leaflets in 14 areas of Gaza, urging residents to temporarily leave their homes.

CNN reporter Ian Lee described the action: “Periodic fire balls illuminate the sky over Gaza. We see rockets screech toward the sky. Minutes later we see an intercepting missile rise from the iron dome, reducing the rocket into confetti of light and fire.

“We’ve seen red tracer rounds fly across the horizon. The repetitive thud of naval guns echoes throughout the coastal strip.”

Earlier in the day, a 4-year-old girl was killed in an Israeli airstrike near the customs building in Khan Younis, Palestinian medical and security sources said, and another airstrike killed a 29-year-old man east of Khan Younis.

Aqsa TV reported that an Israeli was killed and another injured in shelling of Ashkelon and that seven Israeli soldiers were injured in an attack on a military location.

Aqasa TV also reported that Israeli gunboats near Baiet Lahiya north of Gaza strip, fired at the homes of residents.

Palestinian medical and security sources say 240 people have been killed in Gaza and about 1,800 injured. Israel says one of its citizens has died.

Amid all the military action, the Israeli Cabinet planned to meet at 11 a.m. Friday.